The present invention relates to an electrochemical sensor which is indwelled subcutaneously in human being and an animal and continuously measures (monitors) a physical quantity of components within a living organism.
An RT-CGM (Real-Time Continuous Glucose Monitoring) apparatus performs a Continuous Glucose Monitoring (CGM) process for continuously measuring (monitoring) a concentration of glucose contained in a subcutaneous interstitial liquid by employing a biosensor, which has an electrode and an enzyme reacting on the glucose, indwelled subcutaneously.
The RT-CGM device includes, as a basic configuration, a sensor unit and a data receiver which performs data communications with the sensor unit. The sensor unit includes a biosensor and a measuring (monitoring) instrument to which the biosensor is attached. A part of the biosensor is fitted in a fixed state within a housing of the monitoring instrument.
The biosensor is formed in a sheet-like or board like shape. Also, the biosensor has a one end portion formed on a plurality of electrodes and another end portion fixed within the housing for the monitoring instrument. The biosensor is fitted in the monitoring instrument in a state where the one end portion thereof protrudes from the housing for the monitoring instrument. The other end portion of the biosensor is inserted into a living organism of an examinee and is indwelled subcutaneously when the monitoring instrument is attached to the examinee for monitoring the glucose.
Electronic components composing a sensor control unit and a data transmitter are disposed within the housing for the monitoring instrument. The sensor control unit is electrically connected to a plurality of electrodes provided on the biosensor. The sensor control unit controls application of a voltage to between the plurality of electrodes and detection of an inter-electrode current (called a response current) derived from enzyme reaction caused by this voltage application. The data transmitter converts, e.g., a value of the detected response current into a predetermined data communication format and transmits the thus-converted data to a data receiver.
The data receiver includes an computing unit (computer) which computes a glucose concentration by a known technique such as monitoring the glucose concentration in a way that uses a calibration curve on the basis of the response current value received from the data transmitter of the monitoring instrument, and a display device which displays the computed result. The computed result (glucose concentration) is displayed by the display device, thereby the glucose concentration in an interstitial liquid is presented.
The RT-CGM device is capable of continuously acquiring the response current while the biosensor is kept indwelling subcutaneously. Therefore, the data transmitter transmits anytime the response current value per predetermined time (unit time) to the data receiver, and the display device of the data receiver may continuously display time-based variations of the glucose concentration.
There has hitherto existed a biosensor of which the other end portion is formed with portions (called contact pads) serving as electric contacts between the plurality of electrodes and the electronic components within the housing for the monitoring instrument (refer to, e.g., Patent document 1). The contact pad is formed on a per-electrode basis. The other end portion of the biosensor is fixed within the housing in the way of being interposed between components or portions within the housing. On this occasion, the respective terminals (contacts) of the electronic components installed within the housing contact the contact pads, thereby connections between the individual electrodes and the electronic components is established.    [Patent document 1] U.S. Pat. No. 6,973,706 (FIG. 2)
The one end portion of the biosensor is indwelled subcutaneously in the examinee when monitoring the response current, and hence external force is applied depending on how the examinee moves. According to the conventional technology described above, the other end portion is fixed by interposing the other end portion of the biosensor in interior of the housing. Thus, the conventional technology is not structured to absorb the external force applied to the one end portion of the biosensor through the movement of the biosensor. Therefore, there is a possibility that tissues around the one end portion are damaged.
Moreover, if the external force is applied to the one end portion indwelled subcutaneously due to a muscular movement, force acting in a rotating direction occurs on the flat surface of the other end portion with the result that the one end portion deviates in position, whereby the contact between the contact pads and the terminals might lose its preferable state.